This invention relates to apparatus for forming a tire bead, and more particularly to an insert for use with a tire bead forming apparatus for providing a space in the formed bead for receiving the gripped end of the wire after winding of the tire bead has been completed.
In the manufacture of a tire bead, a collapsible rotatable tire bead former is positioned in a starting position and the leading end of a continuous length of wire is supplied to a gripping apparatus which grips the leading end of the wire. Then, the tire bead former is rotated a predetermined number of revolutions to wind the wire around the tire bead former and thereby form a tire bead having a predetermined number of convolutions. After the predetermined number of convolutions has been wound on the tire bead former, rotation of the tire bead former is stopped and the wound wire is severed from the supply of wire. Then, the tire bead former is collapsed to permit the completed tire bead to be removed from the tire bead former.
To dissipate and eliminate the stress concentration in the wire endings area of the tire bead, various treatments of the wire ends are employed. For example, the wire ends are physically treated such as by flattening, tapering, pointing, softening, or otherwise preventing and eliminating point contact between the wire ends of the individual wires and preferably, the inner surface of the body of the tire bead ring. The means of treating the wire ends include grinding, swagging, machining and heat treating such as wire surface welding, brazing and soldering. However, it is believed that such treatment of the wire ends results in substantial reduction of strength efficiency of the bead ring body, thereby defeating the purpose of the wire end treatment.
It has been observed that when a tire bead is manufactured and placed on an expandable mandrel to measure the breaking load and tensile strength of the finished tire bead structure, the tire bead ring breaks at or closely adjacent to the point whereat the termination ends of the tire bead wire are in contact with the inside surface of the tire bead ring or body. Although the precise mechanism of how the tire bead assembly breaks when a breaking load is applied thereto is unknown, it is believed that the wire termination ends may cut into the surface of the convolutions of wire in the bead assembly or sharply bend the adjacent wires to cause breakage of the bead assembly at the wire termination ends thereof.